In motor vehicles having internal combustion engines, the rpm range and the torque range of the engine is imaged on the rpm range and torque range at the wheels via a transmission and, if required, a torque converter (hydrodynamic torque converter with/without bridge clutch or a dry-friction clutch). Here, a transmission output torque for a given transmission output rpm can be realized with various gear ratios.
In U.S. Pat. No. 4,893,526, a desired value for the transmission output torque is determined from the vehicle speed and the position of the accelerator pedal actuated by the driver. In such so-called E-gas systems, the driver of the vehicle does not directly pregive the engine output torque via the accelerator pedal, for example, via a direct coupling of the accelerator pedal to the throttle flap; instead, the driver determines a propulsion torque at the wheels or a transmission output torque with the accelerator pedal position. A desired value for the engine rpm is determined in dependence upon this desired output torque and the vehicle speed. This desired value for the engine rpm is adjusted by the shifting of a continuously variable vehicle transmission. Furthermore, the desired output torque as well as the adjusted transmission ratio are applied for adjusting the engine torque. In lieu of an E-gas system, another system for engine power control, such as an electronic diesel injection control (EDC, Electronic Diesel Control) can be provided.
In the article entitled "Spezial Antriebstechnik", VDI-Zeitschrift, No. 134, March 1992, pages 26 to 49, a description is provided of determining a desired engine rpm in dependence upon throttle flap angle of the vehicle engine. This desired engine rpm is adjusted via an adjustment of a continuously variable transmission. Furthermore, it is described in this article to select the desired engine rpm also in dependence upon different driving programs. Such driving programs take into account the characteristic of the driver. The driver characteristic is represented by more of a consumption optimized or more of a driving power orientated driving style of the driver.
For vehicle drives having a drive unit with an E-gas or another engine power control, a torque converter and a transmission (automatic stepped transmission, automated switching transmission, continuously variable transmission), it is the task of the drive train control to so adjust the operating point of the drive train that the desired torque is available at the transmission output. The operating points of the drive train are characterized by the engine rpm, the engine output torque, the rpm ratio of the transmission, the rpm ratio and the state of the torque converter.
For the determination of the operating point, the entire degree of the efficiency of the drive train, the torque reserve at the transmission output as well as the emission viewpoints are to be considered.
In today's control architectures, the operating point of the drive train is determined by the selection of the transmission ratio via a transmission control or a drive train control. The determination of the desired ratio takes place by means of shift characteristic lines. Starting from the actual gear ratio, a new desired gear ratio is determined while considering the transmission output rpm and the throttle flap position (in torque guided systems, such as in the above-mentioned E-gas systems, while considering the desired transmission output torque). The shift characteristic lines are suitably applied for this purpose for a specific engine-transmission combination. In this way, the operating point of the drive train is fixed for the realization of a transmission output torque at a given transmission output rpm.
In so-called adaptive transmission controls, this operating point can be shifted in dependence upon driver type and/or in dependence upon driving situation in that different shift characteristic lines are applied for different types of drivers and/or driving situations. In this way, the operating point is especially so selected that driver-type specific torque reserves are available at the transmission output. For this purpose, reference is made to U.S. Pat. Nos. 5,157,609 and 5,025,684 as well as ATZ Automobiltechnische Zeitschrift 94 (1992) 9, starting at page 428 and ATZ Automobiltechnische Zeitschrift 95 (1993) 9, starting at page 420.
In continuously variable transmissions, the determination of the desired gear ratio takes place correspondingly via a characteristic field whose input quantities are the throttle flap position and the transmission output rpm.
Such known methods for controlling the drive train are therefore characterized in that:
criteria other than a driver-type specific torque reserve are not systematically considered in the determination of the operating point of the drive train via a determination of the gear ratio by means of shift characteristic lines; PA1 for a specific engine/transmission combination, an application of the shift characteristic lines is necessary which considers characteristics specific to the engine as well as also characteristics specific to the transmission; and, PA1 operating conditions of the engine and transmission deviating from normal operation are not systematically considered in the determination of the gear ratio via shift characteristic lines. PA1 a first value which represents the reserve of the transmission output torque; and/or PA1 a second value which represents the total efficiency of the drive train of the vehicle; and/or PA1 a third value which represents the emission behavior of different toxic components; and/or PA1 a fourth value which represents the sound emission.